Problem: $-\dfrac{3}{8} + \dfrac{5}{4} = {?}$
Solution: $ = - {\dfrac{3 \times 1}{8 \times 1}} + {\dfrac{5 \times 2}{4 \times 2}} $ $ = - {\dfrac{3}{8}} + {\dfrac{10}{8}} $ $ = - \dfrac{{3} + {10}}{8} $ $ = \dfrac{7}{8}$